A tire-pressure control apparatus of such a type is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. H2-20409.
In the tire-pressure control apparatus disclosed in the above-mentioned publication, pulsed air pressure is applied to a tire air chamber via a control valve device; the air pressure within an air passageway leading to the tire air chamber is continuously measured several times by use of a pressure sensor during an air-pressure stable period; i.e., after the air pressure within the air passageway becomes stable; a change rate of the pressure in the air-pressure stable period is determined; and air leakage is determined on the basis of the measured pressure change rate.
However, in the tire-pressure control apparatus disclosed in the publication, the air pressure within the air passageway must be continuously measured several times by use of a pressure sensor, which increases control load. Further, since the air pressure within the air passageway changes depending on travel conditions of a vehicle and other factors, the tire-pressure control apparatus may erroneously determine that air leakage occurs even when no air leaks.